Clamping assembly

ABSTRACT

A clamping assembly has a first component and a second component, which has an essentially cylindrical outer jacket, which is attachable to the first component. The clamping assembly has a support surface supported against the first component, which is able to be clamped against the first component via a clamping sleeve that is slid onto the outer jacket and may be screwed onto the first component, and via a snap ring that comes to rest against a first clamping shoulder formed on the inner wall of the clamping sleeve and against a second clamping shoulder formed on the outer jacket of the second component. The snap ring is configured as a detent that deflects elastically in a radial direction and the outer jacket of the second component is provided with an undercut behind the second clamping shoulder, when viewed in the axial direction, into which the elastically deflecting snap ring is able to be deformed radially inwardly so that the clamping sleeve may be guided over the snap ring when slid onto the outer jacket of the second component and the snap ring is able to be brought into engagement in an annular groove on the inner wall that is configured as an opposing detent.

FIELD OF THE INVENTION

The invention relates to a clamping assembly, such as, for example, foruse on a fuel injector.

BACKGROUND INFORMATION

A clamping assembly of this type is discussed, for example, in GermanPublished Patent Application No. 2 303 506. The clamping assembly shownthere includes, as a first component, a cylinder head of an internalcombustion engine. A fuel injector, representing the second componentand having an essentially cylindrically shaped outer cover, has asupport surface that rests against the cylinder head in a recess of thesame and is clamped in the cylinder head via a clamping sleeve that isconfigured as a hollow screw and via a snap ring that is set in anannular groove of the fuel injector, for which purpose the clampingsleeve has an external thread that may be screwed into an internalthread of the cylinder head. For this purpose, the clamping sleeve has arecess on its end facing the cylinder head that functions as a firstclamping shoulder and in which the snap ring comes to rest when theclamping sleeve is tightened. The section of the annular groove of thefuel injector that faces the cylinder head functions as a secondclamping shoulder. The snap ring is clamped between the first and secondclamping shoulders upon tightening.

In the clamping assembly, the clamping sleeve is slid onto that end ofthe fuel injector, representing the second component, which faces awayfrom the support surface of the first component and is located behindthe snap ring when viewed from the cylinder head. This may require thatthe diameter of the second component behind the snap ring be configuredto be smaller than the inner diameter of the clamping sleeve all the wayaround, so that the clamping sleeve may be slid over the outer jacketwithout a problem. This part of the outer jacket may therefore need tohave no steps, nor any laterally projecting supports. Moreover, theseconditions may require increased cutting and deformation effort in theproduction of the second component. For example, if, in addition, thefirst component should have an external thread and the clamping sleevean internal thread that is screwed together with the external thread ofthe first component, the section of the clamping sleeve provided withthe internal thread may be required to be slid over the outer jacket ofthe second component, which, on the one hand, may require a great amountof play between the internal thread of the clamping sleeve and the outerjacket and, on the other hand, may result in the internal thread of theclamping sleeve being damaged, for example, by pushing against the snapring.

SUMMARY OF THE INVENTION

In an example clamping assembly of the present invention, the clampingsleeve may be slid, from the end of the second component that faces outtoward the support surface of the first component, onto the outer jacketof the second component. Due to the feature that the snap ring may beconfigured as a detent which elastically deflects in the radialdirection, and that the second component has an undercut into which thesnap ring may deform, and that an annular groove accommodating the snapring may be formed on the inner wall of the clamping sleeve as anopposing detent, the clamping sleeve, when it is slid on, may be slid abit past the snap ring, until the snap ring, which is elasticallypretensioned as a result, snaps into the annular groove of the clampingsleeve, thereby captively mounting the clamping sleeve on the secondcomponent. When the clamping sleeve is subsequently screwed togetherwith the first component, the snap ring is drawn out from the undercutand pressed against the clamping shoulder of the second component. Afeature of this is that the threaded section of the clamping sleeve maynot have to be pushed over the snap ring. By using the clamping assemblyof the present invention, a robust attachment of the two components maybe achieved, requiring little assembly effort and also, in particular,little structural space. The components may be joined only aftercomplete machining, so that no captive parts have to be handled duringthe production process.

If the second clamping shoulder is disposed to the side of the supportsurface and functions as an axial delimitation of an annular groove inthe second component, which has a depth that is greater than the wirediameter of the snap ring, and the annular groove has a stop face forthe snap ring opposite the second clamping shoulder, the snap ring maycome to rest against the stop face and automatically deform radiallyinwardly and into the undercut when the clamping sleeve is slid on.

The inner wall of the clamping sleeve may have, at its end that ispressed onto the second component, a peripheral chamfer that facilitatesthe sliding on of the snap ring. When the clamping sleeve is slid on,the chamfer of the clamping sleeve may cooperate with the stop face ofthe second component in such a manner that the snap ring is deformed soas to slide radially inwardly into the undercut all along the chamferwithout the aid of any tools.

The undercut may be made on the second component to be formed by anessentially conical surface bordering on the clamping shoulder, since inthis case, when the clamping sleeve is screwed together with the firstcomponent, the conical surface may exercise a centering effect on thesnap ring, which is snapped into the clamping sleeve, and on theclamping sleeve itself.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section through the clamping assembly of the presentinvention that, in the illustrated example embodiment, is disposed onthe fuel injector of an internal combustion engine.

FIG. 2 is a top view of the snap ring.

FIGS. 3 through 7 show the assembly of the clamping assembly in asimplified representation.

DETAILED DESCRIPTION

FIG. 1 shows a first example embodiment of a clamping assembly of thepresent invention. In this example embodiment, the clamping assembly ismounted on a fuel injector for internal combustion engines, a firstcomponent 1 of the clamping assembly being formed by the magnet assemblyof the fuel injector. Magnet assembly 1 includes a magnetic core havingpole face 10 and coil 8, as well as a valve spring 9, which impinges anaxially movable armature 7 having a tie plate and tie bolt. A valveassembly of the fuel injector represents a second component 2 of theclamping assembly. Valve assembly 2 has a support surface 20 supportedagainst pole face 10 of magnet assembly 1. A recess 29 in supportsurface 20 forms an armature compartment to accommodate armature 7. Themovable armature controls the discharge of fuel from its controlpressure chamber, which in turn controls the injection operation of thefuel injector. As illustrated in FIG. 1, the clamping assembly alsoincludes a clamping sleeve 3 and a snap ring 4.

As may be recognized in the simplified representation of FIG. 3, firstcomponent 2 has, on a part of its length, a cylindrical outer jacket 21that may not need to extend over the entire length of component 2. Inthe example embodiment illustrated here, cylindrical outer jacketsection 21 is delimited by a shoulder 28, for example. Close to asupport surface 20 of second component 2, an annular groove 27 isintroduced in outer jacket 21 of second component 2 so that a narrowsection 25 of outer jacket 21 forms a peripheral collar. Starting fromcollar 25, annular groove 27 forms a second clamping shoulder 22 whichis intended to hold a snap ring 4 and which has, adjacent to it, anundercut 24 in the form of a conical surface having a tapered diameter.The conical surface transitions into a short cylindrical face section,which in turn projects from an annular face arranged opposite clampingshoulder 22 and running perpendicular to outer jacket 21. Annular face23 functions as a stop face for snap ring 4.

Snap ring 4 is illustrated in FIG. 2 and FIG. 3. The snap ring may bemade out of an elastically deflecting material, such as an elasticallyflexible metal and, in the example embodiment illustrated here, has acircular wire cross section. However, other cross-sections may also bepossible. As may be recognized in FIG. 2, the snap ring has an opening41. The angle a subtended by opening 41 is dimensioned in such a mannerthat, on the one hand, snap ring 4 permits radial deflection whileclamping sleeve 3 is being mounted (FIG. 5), but that, on the otherhand, the support angle (360°−a), that is the angle subtended by thesnap ring when it comes to rest against second clamping shoulder 22, isnot too small. In an example embodiment, opening angle a may be between40° and 60°. Elastic element snap ring 4 may be bent outward somewhatwhen being mounted on second component 2 and, using opening 41, beclipped into annular groove 27 of second component 2 or be guided in theaxial direction over peripheral collar 25, as is illustrated in FIG. 4.The elasticity of snap ring 4 is calculated to be large enough so thatit is not permanently deformed in the course of being positioned onsecond component 2 and during subsequent deflection into annular groove27 (FIG. 5). Before clamping sleeve 3 is mounted, snap ring 4 restsagainst stop face 23 in such a manner that it is radially movable, as isillustrated in FIG. 4.

As is recognizable in FIG. 1 and FIG. 5, clamping sleeve 3 has acylindrical inner wall 33 having an internal thread 34. For the sake ofsimplicity, internal thread 34 is not depicted in FIG. 5. Internal wall33 of clamping sleeve 3 has an annular groove 31 and a chamfer 32 on theend facing away from internal thread 34. As illustrated in FIG. 5,clamping sleeve 3 is slid from support surface 20 of second component 2out onto outer jacket 21 until chamfer 32 butts against snap ring 4.When the clamping sleeve is slid further, snap ring 4, which restsagainst stop face 23, is first elastically compressed, sliding radiallyinwardly along chamfer 32, and in the process penetrates into undercut24.

When clamping sleeve 3 is slid further, snap ring 4, which iselastically pretensioned against inner wall 33, snaps into annulargroove 31 on inner wall 33 of clamping sleeve 3, as illustrated in FIG.6. Snap ring 4 is thus encompassed in a press fit over approximatelyhalf of the perimeter by annular groove 31. Clamping sleeve 3 is thencaptively connected to second component 2. Clamping sleeve 3 may bemoved axially back and forth, the axial mobility of clamping sleeve 3being limited by second clamping shoulder 22 and stop face 23. As shownin FIG. 7, clamping sleeve 3 is now slid in the direction of the arrow,counter to the direction of joining indicated in FIG. 5, until snap ring4 comes to rest against second clamping shoulder 22. In the process,snap ring 4 first slides over the conical surface of undercut 24 and isthus automatically centered, together with clamping sleeve 3. In thisposition, clamping sleeve 3, via internal thread 34, is screwed togetherwith external thread 11 of first component 1, as is shown in FIG. 1. Inthe process, support surface 20 of second component 2 comes to restagainst surface 10 of first component 1. When clamping sleeve 3 istightened, second component 2 is clamped against component 1 and isthereby secured on it. The snap ring is clamped between second clampingshoulder 22 and first clamping shoulder 35, which is formed by a sectionof annular groove 31.

The clamping assembly depicted here may be used in multiple forms. In noway is it limited to the example embodiment described above, but,rather, may generally be used in those cases in which a first componentis joined via a clamping sleeve and a snap ring to a second componenthaving a cylindrical outer jacket. In a departure from the exampleembodiment described above, the clamping sleeve may be provided with anexternal thread and the first component may be provided with an internalthread. Moreover, stop face 23, for example, may be omitted if, in theassembly of clamping sleeve 3, snap ring 4 is pressed on using anappropriately configured tool, until it snaps into annular groove 32 ofclamping sleeve 3. Moreover, undercut 24 may be configured using anon-conical face. It may be important for undercut 24, when viewed fromsupport surface 20, to form, behind clamping shoulder 22, an open spacewhich is used to hold snap ring 3, which is elastically compressed inthe radial direction, so that clamping sleeve 3 is able to slide oversnap ring 4 until the latter snaps into annular groove 31.

1. A clamping assembly comprising: a first component; a second componentfastenable to the first component, the second component including asupport surface for supporting against the first component, anessentially cylindrical outer jacket, and a second clamping shoulderformed on the outer jacket, the outer jacket including an undercutbehind the second clamping shoulder in an axial direction as viewedlooking out from the support surface; a clamping sleeve to clamp thesecond component against the first component, the clamping sleeve beingslidable onto the outer jacket and being screwed together with the firstcomponent, the clamping sleeve including an inner wall having a firstclamping shoulder and an annular groove formed on the inner wall; and asnap ring to assist in clamping the second component against the firstcomponent, the snap ring being a detent to elastically deflect radiallyand being snappable into engagement in the annular groove that acts asan opposing detent, the snap ring being pretensioned against the innerwall and deformable radially inward into the undercut so that theclamping sleeve, when slid onto the outer jacket, is guidable from thesupport surface out over the snap ring, the snap ring resting againstthe first clamping shoulder and the second clamping shoulder whenfitted; wherein the clamping assembly is arranged on a fuel injector ofan internal combustion engine.
 2. The clamping assembly according toclaim 1, wherein the second component includes an annular groove havinga depth greater than a wire cross-section of the snap ring, and thesecond clamping shoulder is disposed to a side of the support surfaceand functions as an axial delimitation of the annular groove.
 3. Theclamping assembly according to claim 2, wherein the annular groove ofthe second component includes a stop face for the snap ring arrangedopposite the second clamping shoulder.
 4. The clamping assemblyaccording to claim 3, wherein the clamping sleeve includes a chamferarranged to cooperate with a stop face of the second component so thatthe snap ring that is arranged to come to rest against the stop facewhen the clamping sleeve is slid on is deformable radially and inwardly,sliding into the undercut along the chamfer.
 5. The clamping assemblyaccording to claim 1, wherein the inner wall includes a peripheralchamfer on an end that is slid onto the second component.
 6. Theclamping assembly according to claim 1, wherein the second clampingshoulder is adapted to a shape of a wire cross-section of the snap ring.7. The clamping assembly according to claim 1, wherein the snap ringincludes a circular wire cross-section.
 8. The clamping assemblyaccording to claim 1, wherein the clamping sleeve has an internal threadand the first component has an external thread.
 9. A clamping assemblycomprising: a first component; a second component fastenable to thefirst component, the second component including a support surface forsupporting against the first component, an essentially cylindrical outerjacket, and a second clamping shoulder formed on the outer jacket, theouter jacket including an undercut behind the second clamping shoulderin an axial direction as viewed looking out from the support surface; aclamping sleeve to clamp the second component against the firstcomponent, the clamping sleeve being slidable onto the outer jacket andbeing screwed together with the first component, the clamping sleeveincluding an inner wall having a first clamping shoulder and an annulargroove formed on the inner wall; and a snap ring to assist in clampingthe second component against the first component, the snap ring being adetent to elastically deflect radially and being snappable intoengagement in the annular groove that acts as an opposing detent, thesnap ring being pretensioned against the inner wall and deformableradially inward into the undercut so that the clamping sleeve, when slidonto the outer jacket, is guidable from the support surface out over thesnap ring, the snap ring resting against the first clamping shoulder andthe second clamping shoulder when fitted; wherein the undercut is formedby an essentially conical face that is directly adjacent to the secondclamping shoulder.
 10. A clamping assembly comprising: a firstcomponent; a second component fastenable to the first component, thesecond component including a support surface for supporting against thefirst component, an essentially cylindrical outer jacket, and a secondclamping shoulder formed on the outer jacket, the outer jacket includingan undercut behind the second clamping shoulder in an axial direction asviewed looking out from the support surface; a clamping sleeve to clampthe second component against the first component, the clamping sleevebeing slidable onto the outer jacket and being screwed together with thefirst component, the clamping sleeve including an inner wall having afirst clamping shoulder and an annular groove formed on the inner wall;and a snap ring to assist in clamping the second component against thefirst component, the snap ring being a detent to elastically deflectradially and being snappable into engagement in the annular groove thatacts as an opposing detent, the snap ring being pretensioned against theinner wall and deformable radially inward into the undercut so that theclamping sleeve, when slid onto the outer jacket, is guidable from thesupport surface out over the snap ring, the snap ring resting againstthe first clamping shoulder and the second clamping shoulder whenfitted; wherein the annular groove that is provided as an opposingdetent encompasses a wire cross-section of the snap ring in a press fitover approximately half of a perimeter.
 11. A clamping assemblycomprising: a first component; a second component fastenable to thefirst component, the second component including a support surface forsupporting against the first component, an essentially cylindrical outerjacket, and a second clamping shoulder formed on the outer jacket, theouter jacket including an undercut behind the second clamping shoulderin an axial direction as viewed looking out from the support surface; aclamping sleeve to clamp the second component against the firstcomponent, the clamping sleeve being slidable onto the outer jacket andbeing screwed together with the first component, the clamping sleeveincluding an inner wall having a first clamping shoulder and an annulargroove formed on the inner wall; and a snap ring to assist in clampingthe second component against the first component, the snap ring being adetent to elastically deflect radially and being snappable intoengagement in the annular groove that acts as an opposing detent, thesnap ring being pretensioned against the inner wall and deformableradially inward into the undercut so that the clamping sleeve, when slidonto the outer jacket, is guidable from the support surface out over thesnap ring, the snap ring resting against the first clamping shoulder andthe second clamping shoulder when fitted; wherein the snap ring thatsnaps into the annular groove is clampable between the first clampingshoulder and the second clamping shoulder by screwing together theclamping sleeve and the first component.